Solid variant of aneurysmal bone cyst

Last revised by Karwan T. Khoshnaw on 3 Nov 2022

The solid variant of the aneurysmal bone cyst (ABC) is a rare non-neoplastic and reactive bone lesion. It differs from the classical type of ABC in certain aspects.

The solid variant of ABC has an incidence of ~5% (range 3.4-7.5%) and is found to have slight female predilection (1.5:1) 1,2.

  • histologically, the solid variant of the ABC and giant cell reparative granuloma are similar in appearance and therefore, these terms are interchangeably used 4,5

  • it is similar histopathologically to the solid portion of a classical ABC

  • more than one-third of lesions diagnosed as solid ABCs are non-aneurysmal

  • giant cell reparative granuloma and the solid variant of ABCs have primarily been seen in the craniofacial and small tubular bones of the hands and feet 1-6

  • 30% cases were found in upper extremities 1-6

  • in a long bone, no location is exempt; the most commonly seen location is meta-diaphyseal but lesions have also been reported at the end of long bones, within the cortex, and on the surface 1-6

  • an expansile, eccentric lytic lesion with or without a cortical shell, located in the metadiaphyseal region of a long bone. (In contrast to classical aneurysmal bone cysts, it is not epi-metaphyseal and in 30% of cases it appears non-expansile unlike the classical soap bubble appearance of ABC)

  • variable degree of mineralization

  • T1: iso to hyperintense with respect to muscles with a solid component seen

  • T2

    • heterogeneously hyperintense solid component

    • blood fluid levels can be seen in cystic components (mimicking classical secondary aneurysmal bone cysts) but less often seen

    • bone marrow and soft tissue edema is seen in 50% of cases (distinguishing feature from classical aneurysmal bone cysts)

    • due to the variable degree of mineralization, few T2 hypointense areas can be seen

  • T1 C+: solid enhancement seen (in contrast to smooth septal and rim enhancement seen in classical aneurysmal bone cysts)

Treatment includes cauterisation of the lesion.

  • classical ABC (epi-metaphyseal location with no soft tissue and bone marrow edema on MRI)

  • telangiectatic osteosarcoma: 50% of cases show osteoid mineralization. Endosteal scalloping and aggressive bone destruction with a wide zone of transition favors telangiectatic osteosarcoma over sABC on radiographs. Septal enhancement on post-contrast MRI again favors it

  • brown tumor

  • giant cell tumor is preferred diagnosis over rarely reported sABC, if the lesion is seen at end of long bones

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